<!DOCTYPE html>
<html lang="en">

<head>
    <meta charset="UTF-8">
    <meta name="viewport" content="width=device-width, initial-scale=1.0">
    <title>Document</title>
</head>

<body>
    <label for="input">用户名：</label>
    <form action="index.html">
        <input type="text" id="input" name="uname">
    <input type="submit" value="登陆">
    </form>
    
    <script>
       
        var btn=document.querySelector('button');
        btn.addEventListener('click',function(){
            
            location.href='index.html';   
        })
    </script>
</body>

</html>